This invention pertains to a takeup reel for combined hydraulic hose and electrical cable, and more particularly to such a reel in which a brushless electrical interconnection is provided between cable stored on the reel and a supply of electrical energy external to the reel.
In many instances, it is desirable to be able to provide an electrical interconnection between a pair of relatively rotatable members. In the past, such electrical connection generally has been provided by a plurality of relatively rotating brush elements in a rotatable connector. These, however, have not been altogether satisfactory, in that they often produce electrical arcing with its attendant fire hazards.
One instance in which it is particularly desirable to be able to provide an electrical interconnection between a pair of relatively rotating members is in a takeup reel on which line is stored for supplying energy between a pair of relatively movable parts. An example of such is found in the usual lift truck which has an upright mast on which is mounted a vertically shiftable carriage. The carriage may be adapted to carry various kinds of power-operated equipment, such as a side-shifter, clamping arms, a vacuum grab, etc. Such equipment may be either electrically or hydraulically operated, or require a combination of both forms of energy. In some lift trucks the mast is telescopic, in that the carriage may rise substantially fully the height of the mast, and then the mast itself may be extended telescopically to further raise the carriage.
In such apparatus, a line takeup reel may be mounted on the mast in such a manner that as the carriage moves along the mast, lines connected to the carriage are taken up on the reel, and as the carriage moves away from the reel, lines are paid out. Such a takeup reel generally has a rotatable storage portion for taking up and paying out line, and substantially stationary mounting member secured to the mast about which the storage portion rotates. Electrical energy and/or hydraulic fluid must pass from the substantially stationary mounting member to lines taken up and payed out from the rotatable portion throughout operation of the reel.
Previous devices for providing electrical interconnection between the substantially stationary mounting member and the rotatable storage portion generally have been through brushtype electrical connectors. Since these may produce electrical arcing, they produce a definite fire hazard when used in conjunction with certain hydraulic fluids.
A general object of the present invention is to provide a novel takeup reel having a rotatable storage portion for taking up and paying out line, a mounting member on which the storage portion is mounted for rotation thereabout, and a brushless electrical interconnection between a cable stored on the storage portion and a supply of electrical energy external to the reel, which electrical interconnection is so constructed as to overcome in a simple and economic manner the disadvantages of previous devices set out above.
Another object of the invention is to provide such a novel takeup reel characterized by a compact sandwich construction having axially joined subassemblies including a rotatable storage portion for taking up and paying out windings of a combined hose and cable, a housing for a biasing spring for urging unidirectional relative rotation between the storage portion and the means mounting it for rotation, and another housing for storing windings of an electrical interface cable providing a brushless interconnection between cable stored on the storage portion and an external electrical source. Such construction provides an unusually compact, simply constructed unit.
Yet another object is to provide such a takeup reel which further includes a novel strain relief guide through which a portion of the interface cable passes along a line generally paralleling the rotary axis for the storage portion of the reel, and from which a portion of the cable to be wound in spiral coils exits substantially radially of the assembly. The strain relief guide is mounted for limited rotation about an axis paralleling the axis of rotation for the assembly. Such rotation of the strain relief guide permits the guide to follow generally the lead of the portion of the cable extending outwardly therefrom to minimize bending stress in the cable, regardless of the direction in which it is wound in spiral coils during operation of the apparatus.
Explaining further, the interface cable may be arranged in a spiral extending in one direction in the cable housing when the lines on the storage portion of the reel are fully taken up. On rotation of the reel to pay out line, the interface cable begins to unwind from its spiral. When about half of the length of line on the storage portion of the reel is payed out, the spiral direction of the interface cable may reverse and be wound in this reverse direction until the line is fully payed out. The provision of such reverse spiraling of the interface cable permits maximum pay out of line from the reel with a minimum length of interface cable being required. When the spiraling direction of the interface cable reverses the rotatable strain relief guide rotates with the interface cable toward its new direction to minimize bending stress on the cable.
A more specific object of the invention is to provide such a takeup reel in which the interface cable, in order to accommodate the usual multiple-element electrical cable, includes a plurality of elongate, flexible elements having portions extending axially of the apparatus which are unjoined and extend as a loose bundle through a passage axially of the apparatus. Where the interface cable extends radially outwardly through the strain relief guide the multiple elements are joined in substantially side-by-side relationship to have a flat ribbon-like configuration whereby the same may lie in flat, substantially even spiral coils in the housing. Disposition of the interface cable elements as a loose bundle extending loosely through a passage axially of the assembly minimizes twisting strain on such elements when rotation of the strain relief guide occurs with reverse spiraling of the cable in the housing.
An advantage of the flat ribbon-like portion of the interface cable is that the same will lie in a neat coil within the housing, without tangling or overlapping of the windings during operation.
These and other objects and advantages of the present invention will become more fully apparent as the following description is read in conjunction with the drawings.